Structure uniformity and limits of grain refinement of high purity aluminum during multi-directional forging process at room temperature

The effect of forging passes on the refinement of high purity aluminum during multi-forging was investigated. The attention was focused on the structure uniformity due to deformation uniformity and the grain refinement limitation with very high strains. The results show that the fine grain zone in the center of sample expands gradually with the increase of forging passes. When the forging passes reach 6, an X-shape fine grain zone is initially formed. With a further increase of the passes, this X-shape zone tends to spread the whole sample. Limitation in the structural refinement is observed with increasing strains during multi-forging process at the room temperature. The grains size in the center is refined to a certain size （110 μm as forging passes reach 12, and there is no further grain refinement in the center with increasing the forging passes to 24. However, the size of the coarse grains near the surface is continuously decreased with increasing the forging passes to 24.

Ductility enhancement of EW75 alloy by multi-directional forging

In this study,the Mg-7Gd-5Y-1Nd-0.5Zr alloy can reach a high ductility by the process of multi-directional forging,and the evolution of the microstructure,texture and the mechanical properties were discussed systematically.The results show that after the solutionized sample was multi-forged at 500℃,its grain size can be refined from 292 um to 58 um.As the forging temperature decreased,fine particles precipitated in the matrix.The volume fraction of the particles increased with the forging temperature decreasing,so the nucleation and growth of crystallization were strongly restricted.There was no recrystallization as the forging temperature fell to 410℃,and the severe deformed grains distributed as streamlines perpendicular to the final compression axis.The texture intensity decreased with increasing forging passes.The sample with best ductility was obtained after compressed at 470℃,with an elongation to failure of 21%at room temperature,which is increased by 200%,in comparison with that of the samples in solutionized condition.EBSD results revealed that the mean grain size was 15 um.Refined grains as well as the weakened texture were the key factors to its high ductility.

Microstructure,texture evolution and yield strength symmetry improvement of as-extruded ZK60 Mg alloy via multi-directional impact forging

Multi-direction impact forging(MDIF)was applied to the as-extruded ZK60 Mg alloy,and the microstructure,texture evolution and yield strength symmetry were investigated in the current study.The results showed that the average grain size of forged piece was greatly refined to 5.3μm after 120 forging passes,which was ascribed to the segmenting effect of{10–12}twins and the subsequent multiple rounds of dynamic recrystallization(DRX).A great deal of{10–12}twins were activated at the beginning of MDIF process,which played an important role in grain refinement.With forging proceeding,continuous and discontinuous DRX were successively activated,resulting in the fully DRXed microstructure.Meanwhile,the forged piece exhibited a unique four-peak texture,and the initial<10-10>//ED fiber texture component gradually evolved into multiple texture components composed of<0001>//FFD(first forging direction)and<11–20>//FFD texture.The special strain path was the key to the formation of the unique four-peak texture.The{10–12}twinning and basal slip were two dominant factors to the evolution of texture during MDIF process.Grain strengthening and dislocation strengthening were two main strengthening mechanisms of the forged piece.Besides,the symmetry of yield strength was greatly improved by MDIF process.

Effect of pre-induced twinning on microstructure and tensile ductility in GW92K magnesium alloy during multi-direction forging at decreasing temperature

Effect of pre-induced twinning on the microstructure evolution and mechanical properties of extruded Mg-9.26Gd-2.08Y-0.36Zr(GW92K)alloy have been investigated during multi-direction forging with large strains at decreasing temperature from 400℃ to 300℃.The results showed that,whether there pre-induced twinning existing in the initial microstructure by pre-deformation or not,a mixed microstructure of residual coarse grains and notably refined grains formed under both conditions,combing with some residual coarse grains with less deformation inside grains and lots of dispersed nano-precipitates distributed along refined grain boundaries.However,a significant improvement with the tensile ductility was obtained by the pre-induced twinning in the former alloy.It was suggested that,the pre-induced twinning largely contributed to the grain refinement and lead to an increase in the ratio of fine grain structure which would be responsible for the better properties.Furthermore,during subsequent forging deformation in the pre-deformed sample,the grain refinement mechanism by gradual grain orientation rotation around the surface section in residual coarse-grains was a little different from that by the macro-shear deformation in the as-extruded condition.

Investigation of dry sliding wear properties of multi-directional forged Mg-Zn alloys

Effect of multi-directional forging(MDF)on wear properties of Mg-Zn alloys(with 2,4,and 6wt%Zn)is investigated.Dry sliding wear test was performed using pin on disk machine on MDF processed and homogenized samples.Wear behavior of samples was analyzed at loads of ION and 20 N,with sliding distances of 2000m and 4000m,at a sliding velocity of 3m/s.Microstructures of worn samples were observed under scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and x-ray diffraction(XRD)and the results were analyzed.Mechanical properties were evaluated using microhardness test.After 5 passes of MDF,the average grain size was found to be 30±4p m,22±3 pm,and 18±3 pm,in Mg-2%Zn,Mg-4%Zn,and Mg-6%Zn alloys,respectively,with significant improvement in hardness in all cases.Wear resistance was improved after MDF processing,as well as,with increment in Zn content in Mg alloy.However,it decreased when the load and the sliding distance increased.Worn surface exhibited ploughing,delamination,plastic deformation,and wear debris along sliding direction,and abrasive wear was found to be the main mechanism.

Multi-scale analysis of void evolution in large-section plastic mold steel during multi-directional forging

The void evolution of large-section plastic mold steel during multi-directional forging(MDF)was investigated using multiscale analysis.To simulate the forging process of the plastic mold steel(SDP1 steel)and realize micro-void reconstruction in a representative volume element(RVE),MDF experiment and void-characteristic evaluation of the SDP1 steel were carried out.Traditional upsetting and stretching forging(TUSF)and MDF were simulated to comparatively analyze the evolution of temperature,effective stress,and effective strain.By embedding RVE with a micro-void and using boundary condition by point tracking into the forging process,the single-void evolution in TUSF and MDF was studied.The effect of void orientation on single-void evolution was also investigated.The multi-scale analysis revealed the following results.(1)Compared with TUSF,MDF achieved a higher efficiency in void closure.(2)The closing efficiency of the void increased with the increase in angle h(the angle between the Z and long axes of the void).(3)The closing efficiency increased with the increase in the orientation angle during the forging process.On the basis of the important role of the main stress in each forging step on the void closure,an integral formula of the main stress was proposed.When main compressive-stress integration reached-0.4,the closed state of the void could be accurately determined.

Tribological Characterization of Commercial Pure Titanium Processed by Multi-Directional Forging

This work discusses tribological properties of commercial pure (CP) titanium processed by multi-directional forging (MDF) up to six passes at room temperature and 220 ℃. For this purpose, wear test was conducted by dry sliding pin-on-disk method on the initial and ultrafine grained samples using different stress magnitudes of 1, 1.5 and 2 MPa. The results showed that wear resistance of CP titanium increases after the first pass of MDF in comparison with the initial condition, irrespective of the applied normal stress. For example, the average wear rate of MDFed samples was decreased about 30% and 24%, after first pass at room temperature and 220 ℃, respectively. However, average wear rate of the samples processed by six MDF passes was reduced about 40% at lower normal loads;it was increased about 9% at higher ones as compared to the initial condition. It was also found that the dominated wear mechanisms were abrasive and delaminated at the lower stresses, while the delamination mechanism was intensified and a slight adhesion was observed during the higher applied normal loads.

Simultaneously Enhanced Mechanical Properties and Damping Capacities of ZK60 Mg Alloys Processed by Multi-Directional Forging

In this study,the mechanical properties and damping capacities of cast Mg-5.5 Zn-0.6 Zr(weight percent,ZK60)alloys have been simultaneously improved by a facile multi-directional forging(MDF)processing,and the mechanisms of microstructure evolution and texture modification are systematically investigated.The activation of tension twinning occurs during the initial MDF stage,due to the coarse-grained structure of the as-cast alloy.With increasing MDF passes,the continuous dynamic recrystallization(CDRX)results in a fine equiaxed-grain structure.The typical non-basal texture is formed in the as-MDFed alloy for 6 passes,with the(0001)planes inclined 60°–70°to forged direction and 10°–20°to transverse direction,respectively.A good balance between the strength(~194.9 MPa)and ductility(~24.9%)has been achieved,which can be ascribed to the grain refinement,non-basal texture and fine precipitate particles.The damping capacity is remarkably improved after MDF processing,because the severe deformation increases the dislocation density,which effectively enlarges the sweep areas of mobile dislocations.

Dynamic and Static Aging Precipitation of β-Mg_(17)Al_(12) in the AZ80 Magnesium Alloy During Multi-directional Forging and Subsequent Aging

Dynamic and static aging precipitation of Mg17Al12 phases in AZ80 magnesium alloy was studied by multidirectional forging（MDF） with decreasing temperatures from 410 to 300 ℃ and subsequent aging process. The results show that the morphology of the β-Mg17Al12 phases during forging process dynamically precipitates and aging process（statically precipitation） exhibited granular and laminar shapes, respectively. During the MDF, the inhomogeneous dynamic precipitation of the β-Mg17Al12 phases results in the uniformity on grain size, which is fine in the area with many granular Mg17Al12 phases but the grain is still coarse where there is no Mg17Al12 phases. During the aging process, the morphology of newly formed β-Mg17Al12 phases depends on the structural character of the forged sample. The newly precipitated β-Mg17Al12 phases are coarse laminar and needle-like shape in area with coarse grain. While, the fine newly precipitated β-Mg17Al12 phases are fine granular and needle-like in the area with fine grain.

Simulation of Large Forging Flat-Anvil Stretching Process and Its Optimization

In this paper,a kind of mathematic method for optimizing stretching process of large forgings is proposed.Distributions of effective strain within forged ingots is described by a Gauss function,which is obtained from the simulation of flat-anvil stretching process.Successive stretching is expressed by the superimposing Gauss functions.Optimized stretching process,with both homogeneous and certain strain in the center of forgings,is presented by derivation of this function.The relationship between effective strain and the values of feed is obtained during the successive stretching with a rotation angle of 90° and a feed displacement of 1/2 anvil width.The optimization result is verified by finite element simulation.Optimized value of feed obtained using this method can ensure both uniformity and forging penetration.It provides mathematic model and theoretic basis of optimizing large forging stretching process.

基于混晶评价的大锻件热锻晶粒组织演变

以大型锻件超超临界转子用12%Cr耐热钢为研究对象,采用拔长实验和数值模拟相结合的方式,探究了大锻件热锻过程晶粒组织演变情况。研究表明:热锻后坯料横截面晶粒不均匀性受锻造温度、锻比以及上模压下速度综合影响,小锻比和较低锻造温度与大锻比和较高锻造温度均可改善晶粒不均匀性。基于此,通过拟合得到了12%Cr耐热钢热锻过程坯料横截面晶粒不均匀性与锻造工艺参数之间的量化关系模型;针对大锻件“因大而生”的混晶问题,在现有混晶评价方法的基础上,提出了一种普适性更好的混晶评价方法,即采用统计学方法划分各小组,以每小组晶粒弦长和占总弦长的频率为基础,分别确定大、小晶粒分界组进行评价,对比拔长实验后的混晶组织演变规律验证了该方法的优越性。

大型锻件尺寸在线测量技术研究

随着制造业自动化程度越来越高,传统的尺寸测量设备和方法已难以满足大型高温锻件尺寸在线测量的要求。该文阐述大型高温锻件尺寸在线测量系统的重要性,介绍大尺寸工件在线测量的发展现状,指出目前大型高温锻件尺寸在线测量存在的问题,提出一种基于多目视觉的大型长轴类锻件尺寸测量方法,对测量系统进行架构设计,建立计算的数学模型,总结该测量方法特点与局限性,并指出未来进一步探索的方向。

民族地区中国式现代化:现实基础、核心理念与实践进路

中国式现代化是中华民族在长期探索和实践中所取得的重大成果,是符合中国国情和人民意愿的现代化道路。推进中国式现代化,有利于进一步促进民族地区经济社会的共同发展。新征程上,我们要深刻认识中国式现代化背景下民族地区的发展特点与现状,把握民族地区现代化与中国式现代化的关系,在共同繁荣发展中加快民族地区推进中国式现代化的步伐,不断凝心聚力、奋发进取,进而在中国历史新航程中开辟辉煌未来,不断谱写中华民族伟大复兴的壮丽篇章。

大型锻造液压机锻造成形数智化应用研究

随着工业4.0时代的到来,智能制造已成为制造业转型升级的关键方向。在此背景下,大型锻造液压机作为重要的锻造设备,对生产效率和产品质量的提升尤为重要。研究基于人工智能的大型锻造压机锻造成形全过程多维度数据采集及关键参数智能感知技术,构建一套完整的数据采集系统,实时监控锻造过程中的温度、压力、速度等关键参数,借助云计算平台的强大数据处理能力,对采集到的数据进行深度分析和处理,实现锻造过程参数的实时监测和智能调控,达到锻造过程的数智化应用,为智能制造领域提供理论支持和技术参考。

特大型锻钢件的热处理

特大型锻钢件是能源、冶金、石油化工等行业重型装备的关键基础零部件。其热处理则是其制造工程中难度最大、影响因素最为复杂和风险最高的环节。首次发布的GB/T 42537-2023《特大型锻钢件的热处理规范》规定了特大型锻钢件热处理的技术要求和工艺方法。

航空航天大型锻件质量与生产能耗检测方法

锻造工艺作为航空航天领域生产制造企业至关重要的精密成形方法,被广泛应用于大飞机和火箭上多品种锻件的批量生产,但是对锻件质量要求很高,且锻造工艺能耗巨大,直接影响企业的经济效益,间接造成众多环境污染问题。为争取早日实现我国“双碳”目标以及持续推进制造业转型和能源结构调整的目标,亟需在保证锻件质量要求的基础上采取节能降耗措施。针对航空航天领域以铝合金材料为代表的大型锻件常见缺陷与核心质量要求,将锻造生产流程分解为原材料、备料、加热、锻压和锻后热处理5个主要环节,归纳总结了锻件缺陷及其产生原因和影响机制;系统阐明外观质量、力学性能、晶粒度/平均晶粒尺寸、断裂韧性、残余应力和抗腐蚀能力等质量要求的检测方法的研究现状,为铝合金等金属大型锻件的重要质量检测研究提供指导;同时,针对大型金属锻件锻造工艺能耗管控粗放的特点,从工厂层、装备层、产品层3个层面梳理能耗检测方法并提供提高能效的相关研究思路,为实现航空航天大型锻件节能降耗生产提供指导。在锻造行业高质低耗生产转型发展过程中,该理论方法在以铝合金为代表的大型金属锻件关键质量检测和生产能耗检测方面,具有一定的指导意义。

Enhancing strength and ductility in back extruded WE71 magnesium alloy cylindrical parts by introduction of multi-direction forging process

Magnesium cylindrical parts have relatively poor mechanical properties and distinct anisotropy of microstructure,which hinder their application as structural components.To improve the performance of WE71 cylindrical parts,multi-direction forging(MDF)was introduced before back extrusion,and the microstructure and mechanical properties were investigated.Results of microstructure show that the grain size in the outer of the cylindrical bottom is refined from 30.1 to 27.7μm,the micro structure is more uniform and the dislocation density is higher.The bimodal grain structure is formed in the outer of the cylindrical wall,which is ascribed to the formation of MgsRE phases along grain boundaries.These phases result in the Zener pinning effect on grain boundaries and the reduction of DRX volume fraction.The texture type of the cylindrical bottom is<0001>‖ED and the cylindrical wall is<1010>‖ED,and the maximum pole intensity is 1.986 and 1.664,respectively.Results of the tensile test at room temperature show that combined improved strength and ductility of the cylindrical part is attained after introducing the MDF process.The ultimate tensile strength(UTS),yield strength(YS)and elongation are279 MPa,185 MPa and 12%at the bottom and 299 MPa,212 MPa and 20%at the wall.

大尺寸锻造β型γ-TiAl合金的显微组织与力学性能分析

β型γ-TiAl合金被广泛应用于复杂零件的制备,但在大尺寸单向锻造过程中显微组织和力学性能表现出显著的不均匀性。通过扫描电子显微镜(SEM)、电子背散射(EBSD)和X射线衍射(XRD)分析了合金的显微组织,关注大尺寸锻造的高β相含量Ti-43Al-9V-0.2Y合金的显微组织和力学性能。研究表明,V元素的添加提高了合金的β相含量,增强了热变形能力。锻造技术在有效变形区形成了细小的等轴晶粒组织,而变形死区则仍保留了部分原始层片结构,中心区域的细小等轴晶粒赋予了合金优异的室温性能,尤其是1.42%的室温塑性。高温力学性能分析显示,Ti-43Al-9V-0.2Y合金在700~750℃范围内经历韧脆转变,在脆性断裂温度下具有较高的强度,主要变形机制为加工硬化。在韧性断裂温度下,合金展现出良好的塑性,主要通过动态再结晶和微孔协调变形来实现。

大型薄壁空心构件精密校形工艺研究

针对航天领域大型薄壁空心构件在连续热挤压过程中产生的不良变形问题,提出了充压镦形精密校形工艺。以具有轴向弯曲缺陷的单腔和多腔铝合金挤压件为研究对象,首先,利用有限元仿真探索了关键工艺参数对校形结果的影响,确定了校形后误差值与校形压缩量之间的变化关系。在此基础上,根据校形产品形状设计充压镦形模具,开展空心构件精密校形试验。结果表明,经充压镦形校正后的空心构件具有高度形状精度,满足生产制造标准。充压镦形技术不仅可用于单腔大型薄壁空心构件的精密校形工作,而且可适用于铝合金大尺寸异形多腔构件,有助于满足未来空心构件制造中多样化型号所带来的高效率和高精度要求。